Optical device

Abstract

This invention prevents a degradation in image quality resulting from undesirable reflected light and undesirable transmitted light generated near the ridgeline of the edge portion of an optical element including an aperture blade or an ND filter. The aperture edge of the aperture blade cooperates with the aperture edge of another aperture blade to form an almost rhombic aperture. A small saw-toothed and non-periodic uneven portions having various sizes are formed along two, front and rear ridgelines of the aperture edge and along those of the ND filter. When incident light beams strike the aperture edge of the aperture blade or the edge of ND filter, the uneven portions formed at the ridgeline reflect them in various directions.

1. An optical device employed in a photographing optical system which forms an object image on an image sensor, comprising one plate-like optical element or plural plate-like optical elements, wherein at least one optical element includes an edge portion that forms an aperture or an edge portion that is positioned in said aperture, and non-periodic uneven portions are formed along a ridgeline of said edge portion, the uneven portions being formed in a direction of thickness of said plate-like optical element and substantially parallel to an optical axis of the optical device. 
   
   
     2. The optical device according to  claim 1 , wherein said uneven portions have saw-toothed shape with various sizes. 
   
   
     3. The optical device according to  claim 1 , wherein an end face of said edge portion of said plate-like optical element has a groove with non-periodic shape, and said groove is directed in a direction different from that of said ridgeline. 
   
   
     4. The optical device according to  claim 1 , wherein an end face of said edge portion of said plate-like optical element has a groove with non-periodic shape, and said groove is directed in the same direction as that of said ridgeline. 
   
   
     5. The optical device according to  claim 3 , wherein said non-periodic shape includes saw-toothed shape with various sizes. 
   
   
     6. The optical device according to  claim 1 , wherein said plate-like optical element comprises a plurality of aperture blades, and said aperture blades operate to form said aperture with said edge portion. 
   
   
     7. The optical device according to  claim 1 , wherein said plate-like optical element comprises an optical filter, and said edge portion of said optical filter is positioned in said aperture. 
   
   
     8. The optical device according to  claim 1 , wherein said plate-like optical elements comprise both an optical filter and an aperture blade which forms said aperture with said edge portion, and said edge portion of said optical filter is positioned in said aperture. 
   
   
     9. The optical device according to  claim 8 , wherein one among said aperture blade and said optical filter is moved independently of the other one of among them. 
   
   
     10. The optical device according to  claim 8 , wherein said optical filter is moved together with said aperture blade. 
   
   
     11. The optical device according to  claim 7 , wherein said optical filter comprises an ND filter obtained by forming a light attenuation thin film on at least one surface of a transparent plastic film. 
   
   
     12. The optical device according to  claim 7 , wherein said optical filter comprises a gradation ND filter in which the farther a light transmitting position is away from said edge portion, the lower a light transmittance at that position of said gradation ND filter becomes continuously. 
   
   
     13. An optical device employed in a photographing optical system which forms an object image on an image sensor, comprising:
 one plate-like optical element or plural plate-like optical elements having two generally parallel faces and an edge portion extending between two parallel faces, 
 wherein said edge portion forms an aperture or is positioned in an aperture, and wherein non-periodic uneven portions, formed along a ridgeline of said edge portion, extend from said edge in a direction generally perpendicular to said parallel faces and generally parallel to an optical axis of the optical device.